1. Field of the Invention
This invention relates to a solid state device equipped with a solid state component sealed with a glass material.
2. Description of the Related Art
Conventionally, solid state devices are known which is equipped with a solid state component such as an light emitting diode (LED) element sealed with a transparent resin material such as an epoxy resin. The solid state devices have the problem that the transparent resin deteriorates due to light emitted from the solid state component. In particular, when a group III nitride compound semiconductor to emit light with a short wavelength is used as the solid state component, the transparent resin near the component turns yellow due to high energy light emitted from the component and heat generated from the component itself, so that the light emission efficiency may be reduced with time.
In order to prevent the sealing material from deteriorating, a light emitting device using a glass material as a sealing material is proposed (e.g., JP-A-08-102553 and JP-A-11-177129).
JP-A-08-102553 discloses a light emitting device that an LED element, a wire bonding portion and the periphery of the top portion of a lead are covered with a transparent sealing material made of a glass material. The glass material includes selenium, thallium, arsenic, sulfur etc. added to yield a melting point of 130 to 350° C.
JP-A-11-177129 discloses a light emitting device that a GaN based LED element with a refractive index of about 2.3 is sealed with a low-melting glass with a refractive index of about 2. In this light emitting device, by using the GaN based LED element and the low-melting glass with the refractive index described above, a light to be totally reflected on the interface between the LED element and the low-melting glass can be reduced.
However, the solid state devices in JP-A-08-102553 and JP-A-11-177129 need to be produced by processing the still hard glass material even when using the low-melting glass so that it is impossible to realize the devices by using the conventional resin sealing process. Further, properties and components necessary for realizing the device are not known yet.
Therefore, the inventors checked up issues in realizing the inorganic material sealing process and solved them, where a light emitting device is proposed that can actually obtain effects expected by the glass sealing (e.g., JP-A-2006-108621). JP-A-2006-108621 discloses the light emitting device that is composed of a substrate made of a ceramic material, and a glass sealing portion which is made of a B2O3—SiO2—Na2O—ZnO—Nb2O5 based glass comprising 19 wt % to 30 wt % of B2O3, 0.5 wt % to 15 wt % of SiO2, 1.5 wt % to 8 wt % of Na2O, 44 wt % to 60 wt % of ZnO, and 9 wt % to 19 wt % of Nb2O5. Thus, the glass sealing portion can be prevented from peeling from the substrate and from causing cracks, so that the stable bonding strength between the substrate and the glass sealing portion can be secured. Further, it is confirmed that the glass sealing portion can be prevented from causing a loss in transparency due to crystallization thereof.
Thus, JP-A-2006-108621 teaches the glass material composition to provide the stable glass sealing portion. Further, the inventors have made researches on the weather resistance of the glass sealing portion in addition to the stability so as to improve the durability of the solid state device.